Drowning is the second leading cause of injury-related deaths for children ages 1 to 14. For example, in 1998, more than 1,300 children and young people (ages 0-18) died from drowning. For every child who drowns, another four are hospitalized and 16 receive emergency department care for near-drowning. Among children ages 1 to 4, most drownings occur in residential swimming pools. Most children who drowned in pools were last seen in the home, had been out of sight less than five minutes, and were in the care of one or both parents at the time. Pool fencing is not enough to prevent drowning among young children. In a Center for Disease Control (CDC) funded study, researchers estimated that proper pool fencing would have prevented about one-fifth of drownings among children under 5. This finding suggests that additional strategies (e.g. pool covers, alarms, community education) are needed to prevent drowning (CDC Injury fact book 2001-2002 Water-Related Injuries).
The probability that a near drowning victim will survive decreases significantly with the duration of his submersion. For example, some statistics indicate that a swimmer rescued after only one minute of submersion has a 98 percent probability of surviving while submersion for five minutes or more reduces the survival probability to 25 percent. Even survivors of near drownings may suffer permanent brain damage from extended submersion.
Several solutions have been proposed for detecting drowning events. Approaches include sensors that attach to each individual in the water, wave detectors that detect an object entering the water when the pool is unoccupied but must be inactivated during pool use, and complex video monitoring systems. These solutions have shortcomings such as being impractical, inappropriate for monitoring ordinary swimming episodes, or cost prohibitive. Detecting drowning events by sonar imaging of swimming pools has also been proposed. However, sonar systems are typically quite expensive and therefore unlikely to be widely adopted. Moreover, they focus on monitoring only the top or bottom layers of a swimming pool, thus potentially delaying detection of drowning events during a period critical for the victim. In additions, these systems can be largely inoperative in crowded swimming pools, and they are not adaptable for use in other bodies of water such as lakes.
A current need remains for tools to aid in saving drowning victims. The tools should be inexpensive for widespread adoption and maximum impact. The tools should be detecting drowning events quite promptly. Also helpful would be any means of pinpointing the location of a distressed swimmer in a large or crowded body of water. Such tools should pose a minimum of inconvenience to swimmers. Finally, drowning monitoring systems should be operative under a broad range of conditions, thus ensuring their maximum effectiveness.